I read the first part of this series ('The Sparrow') a short while ago and loved it, so I was keen to read the sequel — particularly as the first part didn't exactly have a happy ending. 'Children of God' follows Father Emilio Sandoz back to the planet of Rakhat, several years after he returned as the only survivor of the first disastrous mission. I think that the author was trying to cater for people who hadn't read the first book, so there's quite a bit of scene setting and recapitulation at the start which is a little tedious if you have read the first part. However, the pace soon picks up, and it becomes completely riveting.
The story ranges widely over the themes of religion, atheism, morality, politics, but I think that it was the biology that gripped me most (for obvious reasons). Doria Russell seems to have put quite a bit of thought into the biological and ecological aspects of the book, and as a result, the Rakhati ecology is at least plausible. True, it's impossible to guess what life on another planet would be like, but the ecology of this fictional planet is at least internally consistent and biologically believable. Rakhat has not one but two sentient species, one of which is more or less domesticated as food for the other. Imagine being able to go to a planet and not only be able to study entirely new forms of plants and animals, but also learn about the thoughts, behaviour, language and culture of two sentient species! I got pretty excited by that idea, and there's plenty of detail for the biology nerd along with missing facts so that you can speculate on the possibilities.
One difficulty with this book was that the story is fragmented over a large number of characters and also over time. The ships taking people to and from Rakhat travel faster than light, so that there are relativity effects on the passage of time. This obviously makes the chronology of events on both Earth and Rakhat rather difficult to untangle, and there are sudden discontinuities as you jump from one story to another. It's not a huge problem, but I did find myself racing through some parts to get back to threads about my favourite characters.
Which brings me neatly to discussing my favourite character. But I _can't_ actually discuss her because it would be a big fat spoiler if you haven't read the book. I will say that she gets all kinds of grief, doom and disaster heaped upon her which I didn't think was adequately resolved. I wanted to know that she was at least content at the end, but her fate was rather summarily dealt with. This sounds like a really big criticism of the book, but it's really just a result of having so many engaging characters — it's impossible to concentrate on them all. The whole thing revolves around Emilio Sandoz, so he gets most of the attention.
In the end, the main question raised by this book is how do we know that we're doing the right thing? You can do something with good or bad intentions, and both can end in disaster. When do dramatic results justify draconian means? It's a very thought-provoking book (don't be put off by the title if you're an atheist like me), and it's well worth a read.